1. Technical Field
The present invention relates generally to protective materials, and in particular, to reactive and adsorptive materials for providing protection from chemical agents and blood agents and methods for providing and using such materials. Also, these materials may be further treated to provide protection from biological agents.
2. Description of Related Art
Agents of chemical warfare have existed for a long time and can generally be grouped into the following three classes: 1) blister/percutaneous agents 2) nerve agents, and 3) blood agents.
1) Blister/percutaneous agents attack the skin and/or mucous membrane tissues external or internal, to the human body, including the inhalation route. The resulting blistering and ulceration is extremely debilitating and can be fatal. Typical of this class is Mustard (labeled as Agent HD) which can be present as a liquid or a gas or within an aerosolized carrier.
These agents were found early on to be readily adsorbed by activated carbon which, when contained within canister beds or immobilized/fixed within or upon various textile substrates, offered the ready capability to adsorb such agents and hold them away from vulnerable body areas of the person to be protected. Activated carbon has been made into and presented as powders, granules, dried slurries, fibers, spherical beads, etc. and is derived from a variety of processes which are performed on organic precursors such as coconut husks, wood, pitch and organic resins. Each process is unique but can be reduced in view to the following steps: (a) carbonizing the organic precursor material to carbon of modest internal surface area (of the order of tens to a few hundred of square meters or surface area per gram of carbon), and then (b) activating this carbon to produce a carbon with many hundreds to low thousands of m2/gm of surface area. Such activated carbon has strong adsorptive abilities. When a material adsorbs something, it means that it attaches to it by chemical attraction. The huge surface area of activated carbon gives it countless bonding sites. When certain chemicals pass next to the carbon surface they attach to the surface and are trapped.
The carbons materials must be fixed within or upon a carrier substrate in order to be rendered into a useful form. Such fixation, whether by way of adhesion or entrapment or some other mode of fixing the carbon on the carrier, must be done deftly enough such that as little as possible of the valuable surface area is obfuscated by the fixation process.
2) The nerve agents are a variety of compounds which can be presented as gases, liquids or secured either in aerosol or other carriers, much as is HD. They attack the human body and interfere with nervous system functioning via immobilization of key enzymes necessary therein, causing death or severe injury. They all operate principally via percutaneous and inhalation routes and are extremely toxic even in miniscule amounts. Typical of such species are Sarin and Soman, often referred to as the G agents (GB and GD). They are also efficiently adsorbed by carbon of high surface area with the same carbon source/process and fixation considerations as discussed above.
3) The blood agents are those species which, when inhaled, dissolve via the lungs in the blood and cause asphyxiation by displacing the oxygen (O2) normally carried by the hemoglobin moieties with more potently binding species known as strong Lewis Bases. Such agents include Hydrogen Cyanide (HCN), Carbon Monoxide (CO), Phosgene (COCl2) and others. The blood agents are minimally and essentially ignorably adsorbed by the activated carbon spoken of above. This is because the blood agents constitute molecules of too low a molecular weight such that their fugacity at normal temperatures exceeds any surface bonding power which the activated carbon can offer. Indeed, although activated carbon is useful for trapping carbon-based impurities (“organic” chemicals), as well as elements like chlorine, many other chemicals (sodium, nitrates, etc.) are not attracted to carbon at all, and therefore pass through unadsorbed. Thus, an activated carbon filter will remove only certain impurities while ignoring others.
It is to be noted that there are some chemical agents which can arguably be either percutaneous, inhalation or blood agents, or some combination of these simultaneously. However, for the purposes mentioned herein, such species would operationally fall into one or more of the modes of handling which are cited above.
Accordingly, there exists a need for materials which have improved adsorptive properties for greater adsorption of impurities and which also have reactive properties to concurrently and effectively neutralize chemical substances which, for example, cannot be adsorbed.